It is known that active pesticidal and other active ingredients can be applied to inert highly absorbent cellulosic granule carriers. Pesticides and pesticidal ingredients in this context comprise any chemical or biological agent or combination of agents that kills plant or animal pests including herbicides, fungicides and insecticides. Pesticides can be applied to such cellulosic granule carriers by spraying the active ingredients in liquid form onto the cellulosic granules so that they penetrate into the granules. So long as the level of the active ingredients does not exceed the liquid holding capacity of the granules, there is generally no need to subject the granules to a drying step following the liquid application. Also, the cellulosic granules may be dusted with pesticides and other active ingredients in powder form. The adhesion of the powders may be enhanced by the application of a liquid adherence agent such as an inert oil.
However, it has not previously been suggested that such treated cellulosic granules could be blended with fertilizer granules and applied as a blended combination product. This is because cellulosic granules are of very different densities (and often different sizes and shapes as well) than the fertilizer granules and would be expected to segregate in a combination product. Such segregation would be expected to occur during blending, bagging, storage and handling, leading to uneven distribution of the granules carrying the actives and the fertilizer granules upon application, as well as possible clogging of the application apparatus.
Nevertheless, combination products of fertilizers and pesticides and other active ingredients that are compatible with the fertilizer are used in the turf industry and elsewhere. Most commonly such combination products are made by spraying liquid pesticides and other active ingredients directly onto NPK fertilizer granules, with minimal amounts of the active ingredients being absorbed and the lion's share adhering to the surface of the fertilizer granules. Alternatively, active ingredients have been applied to the surface of inert carriers (e.g., granulated lime or clay) having a density that generally matches the density of the fertilizer granules and this generally density-matched carrier is then blended with the fertilizer granules. Unfortunately, such coatings of actives on NPK fertilizer granules or conventional inert carriers break down during blending, handling or shipping, creating a significant level of free fine particles carrying high concentrations of the active ingredients. The release of such fine particles carrying high concentrations of pesticide and other active ingredients raises worker safety concerns. The presence of such fine particles of the active ingredients also affects the uniformity of product application and hence the plant phytotoxicity of conventional combination products. There is thus a significant need for a non-segregating carrier for pesticides and other active ingredients in fertilizer combination products that, once treated with the active ingredients is substantially dust-free and doesn't break down during blending, shipping or handling to release fine particles of pesticide and other active ingredients.
One herbicide that is used in current herbicide/fertilizer combination products is oxadiazon. Oxadiazon is a pre-emergence herbicide that provides season-long broadleaf and grass control in turf, ornamental plants and agricultural crops. Current oxadiazon combination products are typically not dust-free following blending, bagging and shipping due to breakdown of the oxadiazon carrier coating, as discussed above. Unfortunately, oxadiazon dust released on application of such combination products tends to coat and adhere to leaf blades increasing the potential for leaf burn. It is thus desirable to deliver the oxadiazon on dust-free granules that will bounce off leaf blades and reach the soil surface without adhering to the leaf blades or other plant surfaces. Current approaches to address this problem have included adding dust control agents such as oils as well as desiccants and anti-clumping agents in combination with the oxadiazon carriers. Unfortunately, these approaches have yielded inconsistent efficiency, dusting, and phytotoxicity results.
Another important factor to consider when formulating pre-emergence herbicides like oxadiazon in fertilizer combination products is particle distribution on the soil surface. Optimal weed control for pre-emergent products requires adequate soil surface coverage. Unfortunately, it is difficult to apply a precise and uniform quantity of fertilizer and oxadiazon per unit area of soil surface using current combination products due to the excessive and unevenly distributed amounts of herbicide and herbicide dust that is present in the combination product.
There is thus a need for heterogeneous blends of fertilizer granules and granules carrying one or more pesticides and other active ingredients that are free of actives dust and that are not subject to segregation of the carrier and fertilizer granules or production of actives dust during blending, handling or shipping. The present invention meets these needs in a unique and unexpected way.